A 2 stroke engine will 4 stroke if it's rich enough but in this case it simply means that it skips one firing stroke before firing on the next and so on. Basically it just means the normal 2 stroke cycle only happens every other rev. The engine makes two totally different sounds when running in either the 2 or 4 stroking and it's quite easy to set the mixture so that it hunts between these two modes once you get familiar with the sounds. So the manual is quite correct when it mentions 2 and 4 stroking but it assumes the modeller understands what's meant. With a 10x6 prop on your 46 it'll begin to 4 stroke at around 12,000 revs or so when it's richened. The safest way though is to have the needle rich enough to be well into a 4 stroke the first time you go to full throttle because you don't want to run it lean. This is the blubbering rich that CGRetired referred to.